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As I have read in the past moisture in your air can destroy consumables in minutes.

Think of it this way, whatever the humidity level is in your ambient air it is increased in the compressed air. With your small compressor running all the time the air doesn't even have a chance to sit in the tank and cool down.

I'm not an expert on the science of a plasma system .... but I know moisture is conductive and having it in the air cannot do anything but hinder the system.

I have what I consider to be the MINIMUM drying system ... a Motor Guard filter.

Read what MILLER says about Plasma Air Supply

Q: What are the necessary air requirements?

A: Compressed air is the most popular gas used for plasma cutting. You can use an air compressor or a bottle of compressed air. The CFM (Cubic Foot per Minute) is important because that is the amount of air that will be distributed per minute and will keep your Plasma machine running consistently. The PSI (Pounds per Square Inch) is the actual air pressure required to operate the machine. All machines need different PSI and CFM. For instance the Miller Spectrum 375 requires 4.5 CFM at 60 PSI to achieve a 3/8-inch rated cut, while the Spectrum 375 X-TREME requires 5 CFM at 90 PSI.

The other gas used is nitrogen, but the only advantages to using it are when cutting stainless steel. You will get a cleaner cut but the cut thickness will be diminished a little. With some exotic metals a gas mixture may be needed.

You will also want to have dry air when operating a plasma cutter. Miller offers a couple of Dryer/Filters that are designed to keep the air dry and clean. Dry air is important because if there is moisture in the line it will travel with the air and exit the end of the torch. This is not necessarily dangerous but will shorten the life of your consumables because the arc will follow the moisture in all directions and erode the tip prematurely.

Air Dryer installed

Well, I visited my local welding supply and dropped $130 on a Motor Gaurd M-26. I figure it's overkill, but at this point I'll try anything. I installed it and to my disappointment my results are only marginally better. I'm still just totally disappointed at the performance of this machine. I don't see how I could ever get a cut near to what it's specs are. I have no idea what to do with this thing, but I certainly don't want it in my garage anymore.

I'm not trying to start anything here, but you may be dealing with operator error here. You just got this machine, granted you did have a problem with the first one, but Miller took care of that, but this is a machine that needs a certain level of skill. You wouldn't expect to buy a TIG welder,and the first bead you ran to look perfect would you?
You've got a great plasma cutter, take the time to learn how to use it before you give up on it.
The learning curve isn't as steep on this machine as a TIG, but you do need to spend a little time learning how to use it before you condemn the tool.

I'm not trying to start anything here, but you may be dealing with operator error here. You just got this machine, granted you did have a problem with the first one, but Miller took care of that, but this is a machine that needs a certain level of skill. You wouldn't expect to buy a TIG welder,and the first bead you ran to look perfect would you?
You've got a great plasma cutter, take the time to learn how to use it before you give up on it.
The learning curve isn't as steep on this machine as a TIG, but you do need to spend a little time learning how to use it before you condemn the tool.

No offense taken. I hear what you are saying. I would just assume my inexperience with the tool would come into play more towards the spec'd limits of the machine. At 1/8" and full power, I would think even a child could make a decent cut without diagonal cut lines and heavy dross on the underside of the cut? No?

No offense taken. I hear what you are saying. I would just assume my inexperience with the tool would come into play more towards the spec'd limits of the machine. At 1/8" and full power, I would think even a child could make a decent cut without diagonal cut lines and heavy dross on the underside of the cut? No?

Lots to take into consideration.

Dross is of course the material cut away by the torch. It has to go somewhere, if there is enough pressure and flow hopefully it will be blown down and away assuming there is clear space beneath for it to fall.

I at times get diag lines as well though not as often as when I first bought the unit. Keep in mind I am not using a " drag tip " though I do at time drag the tip on the metal being cut.

By far the best cuts have been with a standoff as recommended by Millier. Making sure the torch is held so that the tip points STRAIGHT DOWN and I move the troch in a deliberate and constant speed.

The other poster is right. This is a new tool and it will take some practice to learn what it can and cannot do.

Like I said, I get great cuts and I get bad cuts. The good cuts are increasing in frequency with practice. Dross for me is at times a part of the process. I have had no Dross that could not be removed with a slight tap.

Tomorrow if I have time I will show some pics of cuts made in some angle iron. it is either 3/16" or 1/4". I will also do some sheet metal cuts as well.

Give it time and practice. It's not the 375 that is at issue here, I think you'd see the same thing with any plasma cutter the first time out.

Air Compressor

I've read this thread with much interest and since you're pretty much at your "wits end" with this machine might I suggest hooking the machine up to a higher volume air source -- just to test it out.

I'm not trying to be "a pain", but I had the same problem with my cheap import Homier Speedway cutter. It wouldn't cut worth a darn when hooked up to my old 1980's vintage Sears 2HP 20 gal compressor (5.6 CFM @ 90 PSI). Same problems that you're experiencing. I asked around and everyone said that the compressor was adequate. Hence, it must be a problem with the cutter. This went on for weeks.

Then my friend wanted to use it for one of his projects. I went to his house and hooked it up to his Home Depot 60 gal Husky (10.2 CFM @ 90 PSI) and guess what? The darn think worked like a charm -- no dross, just nice clean even cuts all day long.

Since then I purchased a PUMA 5HP 60 gal compressor and my problem is solved.

Just a thought -- I have no experience with the Miller cutter, but knowing the company's customer service model, I would assume that they wouldn't just ship you a replacement machine that wasn't adequately tested before it went out the door.

Clean dry Air

Funny thing happened to me yesterday. I have read thius post since the very beginning and had almost forgot about it. I have a Hypotherm 1000 I bought used and have been happy with it but I always thought it should leave less dross (sound familiar?). Any how I built a bracket to mount it on my shop wall and ran it with a 25 foot flexable air line for the last year or better. Yesterday I plumbed in a new drop tube from my permanent air line so I only have about 2 feet of flexable air line running to it.
Guess what, almost all the dross is gone. I believe that I had too much resistance in the air line that I was using. It is the only explanation I can see as I didn't even change the filter (motorcraft) when I hooked up the new air line to it. Just another one of those hard to believe things in life. Ever notice how your impact works better with a half inch line than a 3/8? Its all volume supply.
Amos